Gas wells produce gas and usually also produce water and petroleum condensates. Typically, in the completion of the well, the wellbore is drilled into a gas bearing formation. Many times a casing is placed in the gas formation. In order to put the formation into production, the casing is perforated to provide access and flow paths to the gas bearing formation. The gas bearing formation can also be fractured utilizing a fracturing fluid to increase production. The purpose of fracturing is to provide additional pathways to allow the flow of gas from the formation to the wellbore. Many times fracturing is done with a fracturing fluid that includes a proppant. The proppant is carried into the fractures with the fracturing fluid and when pressure is released on the fracturing fluid the proppant remains behind and serves to hold open the fractures when the pressure is released. Usually tubing is inserted into the casing to provide a conduit for flow of the production from the well.
In older wells which have been producing for a while, plunger lift techniques can be used to assist production. As a well ages, greater amounts of water and condensates or a portion thereof usually are not expelled from the well and flow back down the wellbore into the near wellbore area. Plunger lift techniques can be used in wells to remove liquids and aid in gas production. Wells using plunger lift are particularly prone to producing water and condensates with some asphaltines as a result of the plunger lift operation.
In intermittent flow wells assisted by plunger lift, there is flowback to the well during the pumping cycle. This flowback can contain asphaltines and other heavies from the petroleum condensates produced. In severe cases these asphaltines can build up on the casing or tubing as well as on the surface of the formation adjacent the wellbore. This can result in the well production being substantially reduced or result in the cessation of production from the well. Water in the formation from flowback can invade the capillaries of the gas bearing formation and result in the blocking or substantial decreasing of the flow of gas from the formation to the wellbore. The formation of scale or deposits on the surfaces of the formation and on the tubing is referred to generally as skin damage.
Thus, there has been a need for a method to clean the area of the gas bearing formation adjacent to the production zone of the wellbore, as well as the casing and tubing, in order to increase production or bring the well back into production. The present invention has the benefit of being an inexpensive and rather rapid method to remove the skin damage thereby cleaning the near wellbore formation of these deposits.
As used in this application, the “near wellbore formation” refers to the volume of the formation which is adjacent to the production zone or zones to be treated and can include all or part of formation through which fissures created by well stimulation (fracturing) extend.